This deck abuses ETB abilities to swarm your opponent with thopters. It was built with Theros rotation in mind.
Sigiled Starfish is necessary to get the right cards and avoid mana problems early game. It is a nice early blocker as well.
Impact Tremors ensures our opponent will eventually lose simply by casting creature spells and spawning thopters.
Mirror Mockery can be used offensively of defensively. If you play it defensively on an enemy creature, it is unlikely that the creature will attack again. At worst, you should be able to trade with your token or stall. If you play it offensively on one of your creature (Chief of the Foundry, Pia and Kiran Nalaar or Whirler Rogue), be careful for removal. It can win you the game pretty fast in combination with Impact Tremors though. It works really well with Whirler Rogue since the two new thopters can be used to make him unblockeable.
Thopter Engineer, Pia and Kiran Nalaar and Whirler Rogue are there to spawn thopters and give them some utility. They work really well with Flameshadow Conjuring and Impact Tremors.
Chief of the Foundry is in there to provide an artifact (that can possibly get haste from Thopter Engineer) to buff that army of flying thopters. I guess it can be quite brutal in combination with Flameshadow Conjuring to suddenly buff by +2/+2. It works on curve with Thopter Spy Network as well.
Thopter Spy Network is our draw engine. It spawns more thopters when you have an artifact which is great with Impact Tremors !
Flameshadow Conjuring is there to go nuts with ETB abilities !
Negate is a filler. This spot should be filled with removal and counterspell adapted to the standard format.
For lands, we have some UU and RR spells, so we really need to fix our mana properly. Foundry of the Consuls sounded like an absolute must include for this deck though. Tomb of the Spirit Dragon could actually be a lifesaver if you are racing in the late game since we are spawning so many thopters.
I have yet to build a sideboard.
